layout: restructure into src/ tests/ android/ scripts/ tools/

- extension/src/{port,platform,codepage} -> src/; native_render -> src/host
  (+ dxt, shaders/); libgr2 -> src/gr2; extension/third_party -> third_party
- extension/tests -> tests/port, libgr2/tests -> tests/gr2
- android-native -> android (build.sh, push-client.sh moved in)
- script -> scripts; tools/40250 -> tools/server; oracle -> tools/granny-oracle;
  perf tools -> tools/perf
- all build trees under build/ (native, release, android, port-gate)
- xrender:: CMake aliases -> mt::; port-map ledger impl paths rewritten

No code changes. ctest 15/15, port_gate macos+android PASS, port_map check 0 errors.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

third_party/cpython-2.7.18/PC/generrmap.c

@@ -0,0 +1,20 @@
+#include <stdio.h>
+#include <errno.h>
+
+/* Extract the mapping of Win32 error codes to errno */
+
+int main()
+{
+    int i;
+    printf("/* Generated file. Do not edit. */\n");
+    printf("int winerror_to_errno(int winerror)\n");
+    printf("{\n\tswitch(winerror) {\n");
+    for(i=1; i < 65000; i++) {
+        _dosmaperr(i);
+        if (errno == EINVAL)
+            continue;
+        printf("\t\tcase %d: return %d;\n", i, errno);
+    }
+    printf("\t\tdefault: return EINVAL;\n");
+    printf("\t}\n}\n");
+}